1. Field of the Invention
The present invention relates generally to a wafer processing system. More particularly, the present invention relates to an integrated chemical mechanical polishing (CMP) system including a CMP wafer polishing unit and a post-CMP cleaning unit coupled to the CMP wafer polishing unit. The inventive CMP system is capable of preventing clogs in the drain piping of the CMP wafer polishing unit.
2. Description of the Prior Art
Chemical mechanical polishing (CMP) techniques are used for planarizing material layers on a wafer in semiconductor industry. In chemical mechanical polishing, slurry is dispensed onto a polishing surface of a polishing pad. Relative movement between the polishing surface and the wafer produces a combined mechanical and chemical effect on the surface of the wafer. This process creates a highly level surface on the wafer. After CMP, the wafer is transferred to a cleaning unit and scrubbed with roller-shaped PVA brushes. During scrubbing of the wafer, a base chemical such as tetramethyl ammonium hydroxide (TMAH) is simultaneously applied onto the surface of the wafer to be cleaned.
One of the major problems facing the CMP process is the clogging in the waste slurry drain piping. It is believed that the agglomeration of abrasive particles, the base chemical crystals from the slurry and/or the polishing pad debris cause clogs in the drain pipe. The cleaning of the clogged drain pipe is time-consuming because the substances that clog the drain pipe are difficult to be removed. Extended maintenance hours may be required in order to ensure that the drain pipe is clean, which increase the down time of the CMP tool as well as the manufacture cost. Moreover, many clogs reside in remote locations in the drain pipe and it is difficult or impossible to find the clogged sites at remote locations in the drain pipe. Sometime, leakage may occur even though the CMP tool is just maintained and the drain pipe is cleaned lately.
Accordingly, there is a need in this industry to provide an improved CMP system and method that better addresses the issues of clogs in the waste slurry drain piping and leakage in the CMP tool.